XTreme EFIS - MGL Avionics

XTreme Operating Manual Page 6
3.1 EFIS display
The EFIS is displayed in a full screen format.
3.1.1 Heading tape
The heading tape is located at the top of the EFIS screen. The heading bug will be displayed in yellow if it is in the view
area else it will turn cyan. The heading bug will always point to the shortest route to achieve the correct heading. The
heading bug can be changed in the EFIS/MFD quick select menu. The heading is corrected for attitude while pitching and
rolling (MGL Avionics AHRS unit required (SP4/SP5)).The Compass parameters can be configured in the “COMPASS
SETUP” menu.
3.1.2 Ground Speed
This is located in the top left corner of the EFIS display. The ground speed value will only be displayed when a valid 2D or
3D GPS fix has been achieved.
3.1.3 Local Pressure Settings (QNH)
This is located in the top right corner of the EFIS display. Turn the rotary control to change the local pressure setting. The
local pressure can be displayed in mB or in “HG.
3.1.4 True Airspeed (TAS)
This is located in the bottom left corner of the EFIS display. TAS is used for most internal calculations where air distance
is of importance.
What is TAS and how is it calculated ?
TAS is indicated airspeed (ASI) compensated for altitude and temperature. Often pilots ignore the effect of temperature
and only take altitude into account when converting ASI to TAS. For practical purposes this is quite accurate and gives a
good reflection on your true airspeed. Keeping in mind that ASI measurement is subject to errors caused by airflow
around your aircraft, there seems little point in taking this calculation to absolute resolution.
Again, we have decided to use a formula often used by pilots. This way the instrument reading will agree with what pilots
are used to.
Add 1.75% of IAS per 1000 ft (304.9 m) increase in altitude above sea level.
We assume here that IAS = RAS (rectified air speed).